In the art of prosthetic dentistry, it is necessary to make removable dies for various operations, as for example, in porcelain veneer crown construction, so that the die may be placed in a swager to better adapt the platinum matrix. A complete cast with removable dies is also desirable to establish the proximal contacts and opposing occlusion, and to check finished restorations. Heretofore, in making a cast of artificial stone or the like, which would be provided with individual stone dies, which are removably replaceable in the cast, the cast could not be fully poured without separating the base from the die. After the cast was partially poured, it was necessary to provide it with a suitable separating medium, such as Vaseline or the like, which would permit the removal of the individual dies from the cast after the completion of the casting. Furthermore, it is very important that each individual die be seated and properly maintained in relation to the cast so that each time that a die is removed, it may be reinserted in proper position in the cast. However, heretofore in the prior art, this presented a problem. While it was usual to provide at least one fiat surface or a groove on the individual stone die and to provide a complementary construction in the cast to serve as a key for proper positioning of the individual die in the complete cast, frequent removal and insertion of the die relative to the cast resulted in chipping or erosion of the cast materials so that the fit gradually became less accurate.

In view of theforegoing, it is an object of the present invention to obviate the disadvantages and deficiencies of the prior art in the formation of removable dies for complete casts.-

It is another object of the present invention to provide a highlynovel-dowel for the formation of dental dies which will permit the formation of the complete cast in asingle continuous casting operation so as to provide for a cast which can be fully poured without the necessity of separating the base from the die.

It is a further object of the present invention to provide a dental dowel whereby the seating and maintenance of the individual dies in their relation to the cast is assured with extreme accuracy.

It is still another object of the present invention to provide a dental dowel construction which allows for easy separation of the individual die from the stone cast and prevents the fracture of the stump.

It is a further object of the present invention to provide a dowel construction for making individual dies which permits entry to all dies and allows for simplified cast trimming.

Other and further objects, advantages and benefits of the present invention will become readily apparent to one skilled in the art from a consideration of the following specification taken in connection with the appended drawings.

In the drawings, which illustrate the best mode presently contemplated for carrying out the invention:

FIGURE 1 is a fragmentary sectional view through a cast and an impression, pursuant to the present invention;

FIGURE 2 is a fragmentary sectional view through a cast formed pursuant to the present invention and illustrates the method of removing the die therefrom;

FIGURE 3 is an exploded view of a dowel pursuant to the present invention;

FIGURE 4 is a view similar to FIGURE 3, showing the parts as displaced by degrees from the position thereof shown in FIGURE 3;

FIGURE 5 is a top plan view of one of the parts illustrated in FIGURE 4 taken on the line 5-5 of FIG- URE 4;

FIGURE 6 is a top plan view of the other of the parts shown in FIGURE 4 taken on the line 6-6 of FIG- URE 4;

FIGURE 7 is a longitudinal sectional view taken through the dowel of the present invention;

FIGURE 8 is a sectional view taken on the line 8-8 of FIGURE 7; and

FIGURE 9 is a sectional view taken on the line 9-9 of FIGURE 3.

Referring now to the drawings in detail and more specifically to FIGURES 3, 4 and 7,there is shown a dowel 10, pursuant to the present invention, intended for use in prosthetic dentistry in the formation of individual dies for teeth. As here shown, the dowel 10 comprises a dowel pin 12 and a complementary dowel sleeve 14. The pin and sleeve are each formed of a suitable material, preferably being cast from a suitable metal.

The pin 12 is provided with a base 16 having an upwardly projecting head 18 of reduced width and a downwardly depending shank 20. The head is provided with a rounded tip 22 and with a rib 24 which extends from the tip to the base 16 and, furthermore, it will be noted that except for the rib 24, the head is ribbed or threaded as at 26 below the tip 22. The shank 20 has three integral portions, namely, an upper portion 28, an intermediate portion 30 and a lower portion 32. It will be noted, as best seen in FIGURE 4, that the intermediate and lower portions 30 and 32 respectively taper inwardly and downwardly from the base 16, but the upper portion 28 does not taper. Furthermore, it will be noted, as best shown in FIGURE 8, that the upper portion 28 has a deformed, circular, horizontal cross-section being provided with the opposing planar surfaces 34. Similarly, the intermediate portion 30 has a deformed, circular, horizontal cross-section having the opposed planar vertical surfaces 36. Furthermore, it will be noted that the upper portion 28 is provided with a vertically extending key 38, which extends downwardly from the base 16. The intermediate portion 30 is provided with the spaced vertically extending keys 40-40 and, similarly, the lowermost portion 32isprovided with spaced vertically extending keys 4242, it being noted that the keys 40 and 42 lie in substantially vertically extending planes which straddle the vertical plane in which the single key 38 extends. It will also be noted that the base 16 is of generally elliptical conformation and lies within a plane which intersects the vertical axis of the pin member 12 at an acute angle.

The sleeve member 14 is a hollow member having a vertically extending bore 44 which extends from the open top 46 to the open bottom 48 thereof. It will be noted that the top 46 is disposed within a plane which has the same angular relationship to the vertical axis of the sleeve 14 that the head 16 has to the vertical axis of the pin 12. Furthermore, it will be noted that at the upper open end 46 thereof the sleeve is provided with a recess or keyway 50 which is complementary to the key 38 on the pin and which is adapted to mate therewith. The sleeve is provided also with an external circumferential rib 52 between the upper and lower ends thereof.

Referring now specifically to FIGURE 7, the pin and sleeve are shown in the mated condition thereof. It will be noted that in said condition the undersurface of the head 16 on pin 12 is in abutting surface relation with the upper end 46 of the sleeve 14, said abutting surfaces being in parallel planes, as previously indicated. Furthermore, it will be noted that the head 16 is larger than the upper end 46 and completely covers the latter and, in fact, projects laterally therefrom as best seen in- FIG- URE 7. Moreover, it will be noted that the only way in which the pin can be inserted in the sleeve is when the key 38 on the pin is inserted into and mates with the keyway 50 defined in the sleeve. Furthermore, it will be understood that due to the previously described formations on the pin, namely, the keys 40 and the keys 42, as well as the deformed circular cross-sections of the pin shank and the tapered conformation thereof, the pin may be inserted within the sleeve even though the tolerances of the exterior surfaces of the pin shank and the inner surface of the bore 44 are not completely equal and accurate, so that even if the tolerances are slightly off, the pin may nevertheless be inserted within the sleeve without binding, but it will be understood that there will still be a sufficient amount of binding action between the opposing surfaces of the pin and the sleeve to retain the pinin position within the sleeve, but nevertheless permit the ready removal of the pin therefrom. Furthermore, it will be noted that when the pin is inserted within the sleeve, the sleeve extends beyond the bottom of the pin at the lower end sleeve portion 54. The function of the sleeve extension 54 will be hereinafter described.

In utilizing the dowel pin of the present invention, an impression 56 of the mouth is first made in the usual manner. Thereafter, a cast 58 is made from the impression 56 and when a sufficient amount of the cast material has been poured into the tooth recess 60, a dowel is inserted into the material within the recess, more specifically, the head 18 of the pin 12 being urged into the casting material within the recess, as best shown in FIG- URE 1. Thereafter, the casting material is fully poured .without the necessity of separating the base from the die, as heretofore required until the sleeves 14 are completely covered with the casting material, it being understood however that blobs of wax or other suitable material are first inserted into the open end 43 of each sleeve so as to prevent the casting material from entering the bore 44 at the lower end portion 54 of the sleeve. After the stone cast 58 has set, the cast is removed from the impression 56 in the usual manner. Thereafter, the cast 58 is trimmed at the bottom surface 62 thereof so as to expose all of the sleeves 14 at the ends 48 thereof, the previously mentioned wax blobs being removed from the bores 44. Proximals on the cast are now separated, preferably by sawing or cutting, after which a suitable tool 64, as shown in FIGURE 2, having a projecting tip or finger 66 which is dimensioned to be inserted within the bore 44 at the lower end portion 54 of the sleeve, is inserted therein until it engages or abuts the lower end portion 32 of the pin. A relatively light tapping upon the tool 64 will then easily separate the pin from the sleeve so that the die 68 provided on the pin may now be removed from the cast 58. The die 68 may be further processed as may be required with the assurance that it can always be returned to its accurately, correctly aligned position within the cast 58 by merely inserting the pin within the sleeve 14, which, of course, is permanently set into the cast, it being noted of course that the pin can be inserted into the sleeve in only one manner, namely, by mating the key 38 with the keyway 50. Furthermore, it will be apparent that the previously described separation of the guide 68 from the cast 58 is facilitated by the enlarged base 16 which, as previously indicated, overlies the upper open end of the sleeve, said base design permitting easy separation of the die 68 from the stone cast 58 and preventing fracture of the stump. Continued insertion and removal of the pin from the sleeve will not affect the positioning of the die 68 on the cast 58 due to the fact that the sleeve is solidly retained in position within the cast and prevented from movement relative thereto by the fact that the embedding. of the rib 52 on the sleeve within the cast retains the sleeve against possible vertical displacement and the embedding of the surfaces which define the keyway 50' in the cast retains the sleeve against possible rotary movement relative to the cast, this retention being aided by the general configuration of the sleeve, whose tapering outline conforms to the tapering outline of the pin. Furthermore, it will be noted that the combination of the threaded portions 26 and the vertical rib 24 on the pin head retains the tooth die 68 in position on the pin head. The threading prevents vertical displacement of the tooth die from the pin and the vertical rib' 24 prevents rotary displacement of the die of the pin head. Furthermore, the enlarged and angularly disposed upper surface of the base 16 provides an enlarged area of securement of the die 68 on the pin and also serves to prevent displacement of the die from the pin.

While I have illustrated and described the presently preferred embodiment of my invention, it will be apparent vthat changes and modifications may be made therein with- :out however departing from the. spirit and scope of the invention as set forth in the appended claims.

I claim:

1. A dowel pin for use in prosthetic dentistry, said pin having a base, a head extending upwardly from said base and a shank extending downwardly from said base, said head being of reduced diameter relative to said shank and having a rounded tip, a vertical rib extending from said tip to said base and circumferential threads in terrupted by said rib.

2. A dowel pin for use in prosthetic dentistry, said pin having a base, a head extending upwardly from said base and a shank extending downwardly from said base, said shank having an upper portion of constant diameter, an intermediate portion and a lower portion, said intermediate and lower portions'tapering inwardly downwardly from said upper portion, said intermediate portion having raised vertical rib means.

3. A dowel pin as in claim 2, and said lower portion having raised vertical rib means.

4. A dowel pin as in claim 3, each of said rib means being spaced vertical ribs, said spaced ribs on said intermediate and lower portions being disposed in' vertical planes which straddle the vertical plane in which said key is disposed.